The specific aims of this study will be: (1) To evaluate and compare normal subjects and RVH patients using MRI- measured values of RV volume (V), mass (M), M/V ratio, mechanical function (wall strain), and hemodynamics. We predict there will be significant differences in all parameters between these two groups. (2) To evaluate the predictive value of RV mechanical and hemodynamic indices, both with respect to predicting functional recovery after therapy and in predicting subsequent deterioration. (3) Assess the impact of redevelopment of RVH on clinical status. Test whether the return of RVH, after initial regression, correlates with or predicts a deteriorating condition. (4) Assess the relationship between hypertrophy regression and afterload reduction after medical or surgical therapy. Statistical testing will ascertain whether or not the two are directly proportional. (5) Compare the time course of remodeling (RVH, M, V, M/V, global and regional mechanical function) between groups treated surgically for pressure overload (PTE and PPH) and combined pressure/volume overload (atrial septal defect). Slower remodeling in the pressure/volume overload group would suggest serial hypertrophy which resolves over a longer period of time.